Insight into the corrosion inhibition of new amino-acids as efficient inhibitors for mild steel in HCl solution: Experimental studies and theoretical calculations

Abstract

Two organic compounds namely, Phenylalanine (P1) and Aspartic acid (P2) have been studied for inhibiting mild steel (MS) corrosion in molar hydrochloric acid solution. The Anti-corrosion activity has been evaluated using electrochemical impedance spectroscopy (EIS), potentio-dynamic polarization (PDP), Density Functional Theory (DFT), Monte-Carlo Simulation (MCS) and Molecular Dynamic Simulation (MDS). The corrosive solutions were analyzed by UV–visible spectrometry (UV–vis). The surface of MS after the corrosion tests was analyzed by Scanning Electron Microscopy (SEM). The inhibition efficiency of the two amino acids (P1 and P2) increased by the increase in their concentration and reached an optimal value of 87% and 89% for P1 and P2 respectively. Their adsorption mechanism was consistent with the isotherm Langmuir. Polarization measurements led to the conclusion that the two compounds act as mixed inhibitors. UV–visible shows that the addition of the two compounds decreases the dissolution of ferric ions in the corrosive solutions. Scanning Electron Microscopy (SEM) images show that both inhibitors were well adsorbed on the MS surface. Computational approaches of the metal-inhibitor interaction type were studied and interpreted using DFT, MCS and MDS.